[libc++] Add the C++17 <memory_resource> header (mono-patch)
This patch is the rebase and squash of three earlier patches.
It supersedes all three of them.
- D47111: experimental monotonic_buffer_resource.
- D47358: experimental pool resources.
- D47360: Copy std::experimental::pmr to std::pmr.
The significant difference between this patch and the-sum-of-those-three
is that this patch does not add `std::experimental::pmr::monotonic_buffer_resource`
and so on. This patch simply adds the C++17 standard facilities, and
leaves the `std::experimental` namespace entirely alone.
Differential Revision: https://reviews.llvm.org/D89057
NOKEYCHECK=True
GitOrigin-RevId: 243da90ea5357c1ca324f714ea4813dc9029af27
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index b010213..6a8c61b 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -48,6 +48,7 @@
- Declarations of ``std::c8rtomb()`` and ``std::mbrtoc8()`` from P0482R6 are
now provided when implementations in the global namespace are provided by
the C library.
+- Implemented ``<memory_resource>`` header from C++17
Deprecations and Removals
-------------------------